System for Heart Performance Characterization and Abnormality Detection

ABSTRACT

A system for heart performance characterization and abnormality detection includes an acquisition device for acquiring an electrophysiological signal representing heart beat cycles of a patient heart. A detector detects one or more parameters of the electrophysiological signal of parameter type comprising at least one of, (a) amplitude, (b) time duration, (c) peak frequency and (d) frequency bandwidth, of multiple different portions of a single heart beat cycle of the heart beat cycles selected in response to first predetermined data. The multiple different portions of the single heart beat cycle being selected from, a P wave portion, a QRS complex portion, an ST segment portion and a T wave portion in response to second predetermined data. A signal analyzer calculates a ratio of detected parameters of a single parameter type of the multiple different portions of the single heart beat cycle. An output processor generates data representing an alert message in response to a calculated ratio exceeding a predetermined threshold.

This is a non-provisional application of provisional application Ser.No. 61/051,777 filed May 9, 2008, by H. Zhang et al.

FIELD OF THE INVENTION

This invention concerns a system for heart performance characterizationand abnormality detection by calculating ratios of detected parametersof multiple portions of a single heart beat cycle of anelectrophysiological signal.

BACKGROUND OF THE INVENTION

Different portions of cardiac electrophysiological signals representactivities and functions of different cardiac tissue and circulationsystems. Usually, surface ECG signal analyses based onelectrophysiological activity (such as ECG signals and intra-cardiacelectrograms) and time domain parameters of waveforms are utilized forcardiac arrhythmia detection and diagnosis, such as P wave distortionfor detection of atrial fibrillation (AF) and ST segment changes formyocardial ischemia and infarction. However, known systems for cardiacarrhythmia identification and analysis based on ECG signals aresubjective and need extensive expertise and clinical experience foraccurate interpretation and appropriate cardiac rhythm management. Earlyarrhythmia recognition and characterization of myocardial ischemia andinfarction, for example, is desirable for rhythm management of cardiacdisorders and irregularities. Known systems analyze waveformmorphologies and time domain parameters associated with cardiacdepolarization and repolarization, such as P wave, QRS complex, STsegment, T wave, for cardiac arrhythmia monitoring and identification.Some known systems apply sophisticated mathematical theories tobiomedical signal interpretation, such as for frequency analysis,symbolic complexity analysis and nonlinear entropy evaluation, andgenerate a pathology index for qualitative cardiac arrhythmiacharacterization. The known systems fail to provide adequate informationon tissue mapping and arrhythmia localization and are subjective andburdensome to use for clinical data interpretation and proper cardiacrhythm management.

Known systems typically analyze time characteristics (amplitude,latency) or frequency domain (power, spectrum) changes but these oftenfail to accurately capture and characterize small signal changes in aportion (P wave, QRS complex, ST segment) of a heart beat cycle.Consequently, known systems may fail to detect arrhythmia or initiate afalse alarm (for example, or indicate a FN (false negative)). Apercentage of false negative results represents patients who do havedisease X, but for whom a screening test wrongly indicates they do nothave disease X. Also known systems relying on amplitude (voltage) changedetection may be inaccurate for cardiac function evaluation andpathology diagnosis. Time domain and frequency domain parameter basedanalysis fails to provide comprehensive detailed indication of severityof pathology, location of abnormal tissue (such as muscle, chamber) andfail to associate signal frequency variation with cardiac pathologicalfunctional changes and may not adequately capture a signal portion (suchas a region of interest (ROI) in cardiac electrophysiological signals).Known systems are typically unable to quantitatively capture andcharacterize changes, and predict a pathological trend such as apathology trend from low risk to medium, and then to high risk (severeand fatal) rhythm (especially a VT growing arrhythmia). Further, noiseand artifact sensitivity and stability impairs arrhythmia detection ofknown cardiac function monitoring systems. A system according toinvention principles addresses these deficiencies and related problems.

SUMMARY OF THE INVENTION

A system improves precision and reliability of analysis and diagnosis ofcardiac electrophysiological activities by calculating ratios ofdifferent portions of a cardiac signal to determine an accurate time,location and severity of cardiac pathology and events. A system forheart performance characterization and abnormality detection includes anacquisition device for acquiring an electrophysiological signalrepresenting heart beat cycles of a patient heart. A detector detectsone or more parameters of the electrophysiological signal of parametertype comprising at least one of, (a) amplitude, (b) time duration, (c)peak frequency and (d) frequency bandwidth, of multiple differentportions of a single heart beat cycle of the heart beat cycles selectedin response to first predetermined data. The multiple different portionsof the single heart beat cycle being selected from, a P wave portion, aQRS complex portion, an ST segment portion and a T wave portion inresponse to second predetermined data. A signal analyzer calculates aratio of detected parameters of a single parameter type of the multipledifferent portions of the single heart beat cycle. An output processorgenerates data representing an alert message in response to a calculatedratio exceeding a predetermined threshold.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a system for heart performance characterization andabnormality detection, according to invention principles.

FIG. 2 illustrates cardiac conduction voltage potentials andcorresponding regions responsible for the signals.

FIG. 3 illustrates a relationship between heart chamber, circulation anda cardiac electrogram signal.

FIG. 4 shows a table indicating signal portion ratios used for heartperformance characterization and abnormality detection, according toinvention principles.

FIG. 5 illustrates signal portion ratio based analysis for a myocardialischemia case which is at the second diagonal of LAD (left anteriordescending) region, according to invention principles.

FIG. 6 shows a flowchart of process employing cardiac signal portionratio analysis used by a system for heart performance characterization,according to invention principles.

FIG. 7 shows an artificial neural network (ANN) employed in a system forheart performance characterization using cardiac signal portion ratioanalysis, according to invention principles.

FIG. 8 shows a flowchart of process performed by a system for heartperformance characterization and abnormality detection, according toinvention principles.

DETAILED DESCRIPTION OF THE INVENTION

A system employs cardiac signal portion ratio analysis of cardiacelectrophysiological signals (including surface ECG signals andintra-cardiac electrograms) to improve characterization and diagnosis ofcardiac electrophysiological activities. The system calculates ratios ofdifferent portions of cardiac signals and uses predetermined mappinginformation to associate particular ratio values to a correspondingparticular medical condition and determine an accurate time, locationand severity of cardiac pathology and events. The system is used toaccurately and reliably identify cardiac disorders, differentiatebetween cardiac arrhythmias, characterize pathological severity, predictlife-threatening events, and evaluate drug delivery and treatmenteffects. The system extracts and characterizes arrhythmia pathologyinformation in cardiac signals and compares and diagnoses a portion ofcardiac signals indicating activities of heart tissue in a region ofinterest (ROI) using a ratio between P wave to QRS complex and STsegment to P wave, for example. The ratio values enable clinical cardiacstatus evaluation of a patient.

The system performs a signal portion multi-ratio based calculation andanalysis to capture and characterize cardiac function relatedinformation and in one embodiment employs an artificial neural network(ANN). A signal portion ratio determination includes time domain signalportion ratio calculation (such as P wave vs. QRS complex, QRS complexvs. ST segment, for example) and frequency domain signal portionanalysis (dominant frequency ratio, principal frequency peak ratio). Thetime domain analysis captures and characterizes signal distortion andcardiac functional abnormality in a signal pathway. Frequency portionratio analysis is used to diagnose and characterize energy andexcitation conduction and variation in cardiac chambers, tissue andcirculation pathways. An ANN system is used for multi-parameter analysisand calculation and provides improved sensitivity and diagnosisstability for cardiac status monitoring and evaluation. The systemsignal portion ratio calculation and analysis advantageously employsrelatively limited computation and power resources and may beimplemented in a wide variety of patient monitors and implantablecardiac devices.

A processor as used herein is a device for executing storedmachine-readable instructions for performing tasks and may comprise anyone or combination of, hardware and firmware. A processor may alsocomprise memory storing machine-readable instructions executable forperforming tasks. A processor acts upon information by manipulating,analyzing, modifying, converting or transmitting information for use byan executable procedure or an information device, and/or by routing theinformation to an output device. A processor may use or comprise thecapabilities of a controller or microprocessor, for example, and isconditioned using executable instructions to perform special purposefunctions not performed by a general purpose computer. A processor maybe coupled (electrically and/or as comprising executable components)with any other processor enabling interaction and/or communicationthere-between. A user interface processor or generator is a knownelement comprising electronic circuitry or software or a combination ofboth for generating display images or portions thereof. A user interfacecomprises one or more display images enabling user interaction with aprocessor or other device.

An executable application, as used herein, comprises code or machinereadable instructions for conditioning the processor to implementpredetermined functions, such as those of an operating system, a contextdata acquisition system or other information processing system, forexample, in response to user command or input. An executable procedureis a segment of code or machine readable instruction, sub-routine, orother distinct section of code or portion of an executable applicationfor performing one or more particular processes. These processes mayinclude receiving input data and/or parameters, performing operations onreceived input data and/or performing functions in response to receivedinput parameters, and providing resulting output data and/or parameters.A user interface (UI), as used herein, comprises one or more displayimages, generated by a user interface processor and enabling userinteraction with a processor or other device and associated dataacquisition and processing functions.

The UI also includes an executable procedure or executable application.The executable procedure or executable application conditions the userinterface processor to generate signals representing the UI displayimages. These signals are supplied to a display device which displaysthe image for viewing by the user. The executable procedure orexecutable application further receives signals from user input devices,such as a keyboard, mouse, light pen, touch screen or any other meansallowing a user to provide data to a processor. The processor, undercontrol of an executable procedure or executable application,manipulates the UI display images in response to signals received fromthe input devices. In this way, the user interacts with the displayimage using the input devices, enabling user interaction with theprocessor or other device. The functions and process steps herein may beperformed automatically or wholly or partially in response to usercommand. An activity (including a step) performed automatically isperformed in response to executable instruction or device operationwithout user direct initiation of the activity. Workflow comprises asequence of tasks performed by a device or worker or both. An object ordata object comprises a grouping of data, executable instructions or acombination of both or an executable procedure.

FIG. 1 shows system 10 for heart performance characterization andabnormality detection. System 10 uses different portions of a cardiacsignal to diagnose electrophysiological activities of the heart tissueand pathways. System 10 includes one or more processing devices (e.g.,workstations, computers or portable devices such as notebooks, PersonalDigital Assistants, phones) 12 that individually include memory 28, userinterface 26 enabling user interaction with a Graphical User Interface(GUI) and display 19 supporting GUI and image presentation in responseto predetermined user (e.g., physician) specific preferences. As well asdevice 12, system 10 also includes at least one repository 17, andelectrophysiological signal acquisition device 15, signal analyzer 19,detector 34, comparator 31 and output processor 36 intercommunicatingvia network 21. In another embodiment these units may be embodied in oneor more processing devices. Display 19 of processing device 12 presentsdisplay images comprising a GUI. At least one repository 17 storeselectrophysiological data, patient parameters, derived parameters andcalculated ratios. Repository 17 further includes mapping informationassociating particular ratio values with a corresponding particularmedical condition and usable to determine an accurate time, location andseverity of cardiac pathology and events. Repository 17 also includesmedical image studies for patients in DICOM compatible (or other) dataformat. A medical image study individually includes multiple imageseries of a patient anatomical portion which in turn individuallyinclude multiple images.

Acquisition device 15 acquires an electrophysiological signalrepresenting heart beat cycles of a patient heart. Detector 34 detectsone or more parameters of the electrophysiological signal of parametertype comprising at least one of, (a) amplitude, (b) time duration, (c)peak frequency and (d) frequency bandwidth, of multiple differentportions of a single heart beat cycle of the heart beat cycles selectedin response to first predetermined data. The multiple different portionsof the single heart beat cycle are selected from, a P wave portion, aQRS complex portion, an ST segment portion, a T wave portion and a Uwave portion in response to second predetermined data, for example.Signal analyzer 19 calculates a ratio of detected parameters of a singleparameter type of the multiple different portions of the single heartbeat cycle. Output processor 36 generates data representing an alertmessage in response to a calculated ratio exceeding a predeterminedthreshold.

FIG. 2 illustrates cardiac conduction voltage potentials andcorresponding regions responsible for the signals. Significant actionrelated voltage potentials within a heart occur in two procedures,depolarization and repolarization, within the four heart chambers. Theaction voltage potentials accumulate and determine a heart electrogram203, known as an ECG (from a body surface) or intra-cardiacelectrograms. Hence different portions of electrograms represent cardiacactivities of a corresponding heart area and tissue. For example, a Pwave represents voltage potential and activities of atrial tissue andmuscles while a QRS complex represents transition of cardiac excitationfrom atrium to ventricle. A single heart beat signal is segmented intodifferent parts 207 including, P wave, QRS complex, ST segment, T wave,and U wave portions. In system 10 (FIG. 1) ratio calculation andcomputation is advantageously also performed on combinations of segments209, including, PR segments, QT segments, TU segments and RT segments,for example. The calculated ratios indicate a comparison of differentaction (and voltage) potential regions and are advantageously used toidentify a location of abnormality and arrhythmia.

FIG. 3 illustrates a relationship between heart chamber, circulation anda cardiac electrogram signal. Electrogram signal 312 is segmented inresponse to cardiac procedure type, specifically depolarization orrepolarization types. A P-wave segment corresponds to atrialdepolarization cardiac procedure 303, a QRS segment corresponds toventricular depolarization cardiac procedure 307 and a T-wave segmentcorresponds to ventricular cardiac procedure 309. System 10 (FIG. 1)compares cardiac procedures and associated signal voltage ratios todetermine time of occurrence within a heart cycle and cause of medicalconditions.

FIG. 4 shows a table indicating advantageous signal portion ratioscalculated by signal analyzer 19 (FIG. 1) used for heart performancecharacterization and abnormality detection as well as cardiac functionmonitoring and analysis. System 10 detects and characterizes a cardiacmalfunction by performing signal portion comparison using calculatedratios and by using mapping information associating particular ratiovalue ranges, cardiac location and demographic data (including age,weight, height, gender and pregnancy status) with cardiac malfunctionand malfunction location in cardiac tissue. The mapping informationfurther identifies a time of occurrence of a malfunction within a heartcycle, as well sequence and severity of the malfunction (e.g. anarrhythmia). System 10 continuously monitors signal portion ratiochanges using different kinds of signal ratios for signal segmentanalysis and diagnosis to detect change in heart activity and functions(especially malfunction and arrhythmias, such as delayed conduction).System 10 compares parameters of a P wave and QRS wave (such as timeinterval, frequency, amplitude magnitude), for example, to provide aphysician analytical information concerning a ratio between atrium andventricle, facilitating medical condition detection and prediction.

Different cardiac signal portions represent electrophysiologicalactivities occurring in different portions of a heart, such as P wave isassociated with atrium activity. Signal analyzer 19 performs differentkinds of analysis and indexing including determining, signal portionmaximum amplitude in the time domain, signal portion time duration,signal portion spectrum, signal portion maximum amplitude in thefrequency domain, bandwidth of a signal portion (e.g., 20-30 Hz) andsignal portion energy. Signal analyzer 19 adaptively hierarchicallyprioritizes or weights signal analysis results and indexes for use inidentifying particular medical conditions. Signal analyzer 19 adaptivelyselects one or more signal portion ratios to calculate, from the ratiosof FIG. 4, such as P vs. QRS or QRS vs. P. Signal analyzer 19automatically selects one or more ratios to calculate in response todata indicating a clinical application, procedure or medical conditionbeing investigated and/or in response to user data entry. For example,for an Atrial Fibrillation (AF) condition, signal analyzer 19 selects Pvs. QRS ratio since the QRS signal portion is stable. While for aventricle Tachycardia condition, QRS vs. P may provide a better and morelinear analysis. A ratio P wave vs. ST segment is usually utilized todetect and characterize myocardial ischemia and infarction, for example.

Signal analyzer 19 may also perform signal portion analysis usingcombined signal portions, such as a signal portion from P wave to R wave(PR portion) and a PT combined portion and a QU combined portion andother combined portions and ratios as indicated in Table I. The combinedsignal portions also comprise combinations of different signal portionsdetermined by a user or automatically by signal analyzer 19 in responseto data indicating a clinical application, procedure or medicalcondition being investigated and/or in response to user data entry.

TABLE I Combined signal PR Segment QT Segment TU Segment PR Segment — QTvs. PR TU vs. PR QT Segment PR vs. QT — TU vs. QT TU Segment PR vs. TUQT vs. TU —

Signal analyzer 19 adaptively selects signal portions to use in ratiocomputation that are sensitive to arrhythmia or cardiac malfunction, forexample, in response to data identifying a medical condition (such as apatient disease history in a medical record). Signal analyzer 19 usesboth time domain and frequency domain based signal ratio calculation andanalysis and calculates a time duration ratio of signal portions as afirst index for use in analysis and quantification of cardiac status.Signal analyzer 19 also calculates other parameter ratios as indexes forarrhythmia localization and severity characterization, such as aspectrum ratio, dominant frequency ratio, peak amplitude or frequencyvalue ratio and amplitude and frequency range ratios. The differentkinds of signal portion ratio indexes and calculations are weighted andprioritized in one embodiment. An ANN based cardiac conditionidentification and decision system employs a combination of multi-indexand ratio analysis. The tables of FIG. 4 and Table I show differentkinds of combination of signal portions and corresponding ratiosenabling signal analyzer 19 to track small changes inelectrophysiological activities within cardiac tissue.

FIG. 5 illustrates signal portion ratio based analysis for a myocardialischemia case which is in the second diagonal of LAD (left anteriordescending) region circulation tissue 503. The example shows monitoringand detection in step 505 of a known cardiac arrhythmia and pathologyduring repolarization, for example, based on a corresponding ratio (suchas ST segment vs. P wave). Signal analyzer 19 (FIG. 1) in step 507calculates, in the time domain and frequency domain, an ST segment vs.QRS wave ratio of detected parameters of a single parameter type ofdifferent portions of a single heart beat cycle. In the time domain, thesingle parameter type comprises an amplitude or time duration and in thefrequency domain comprises a dominant frequency or a principal frequency(as described later), for example. In step 511 signal analyzer 19automatically identifies a particular medical condition indicated bycalculated ratios using mapping information associating particular ratiovalue ranges, cardiac location and demographic data (including age,weight, height, gender and pregnancy status) with cardiac malfunctionand malfunction location and severity in cardiac tissue. Thereby signalanalyzer 19 detects and localizes an unknown cardiac disease within thecardiac tissue and detects a malfunction time of occurrence within aheart cycle and trend of the malfunction. The signal portion ratioanalysis is applied to a single lead ECG signal (such as Lead I/II/III)as well as to multi-lead ECG and EP signals. Signal analyzer 19 usesmulti-channel signal portion ratios and the mapping informationassociating ratios with cardiac locations to derive more detailedinformation and status of the cardiac tissue and function.

FIG. 6 shows a flowchart of process employing cardiac signal portionratio analysis used by system 10 (FIG. 1) for heart performancecharacterization. System 10 in step 603 acquires cardiacelectrophysiological signals (including surface ECG signals orintra-cardiac electrograms). Cardiac signals, e.g., intra-cardiacelectrograms are acquired from a multi-channel intra-cardiac catheterand digitized by a patient monitoring system and sent to system 10 instep 605. In step 607 detector 34 detects selected multiple differentportions of a single heart beat cycle and in step 609, detector 34detects one or more parameters of the digitized and bufferedintra-cardiac electrograms of multiple different portions of a singleheart beat cycle. Parameter types include, amplitude, time duration,peak frequency and frequency bandwidth, for example and the multipledifferent portions of the single heart beat cycle include, a P waveportion, a QRS complex portion, an ST segment portion, a T wave and a Uwave portion.

In step 613, signal analyzer 19 calculates a ratio (selected from theratios of FIG. 4 or Table I) of detected parameters of a singleparameter type of the multiple different portions of the single heartbeat cycle in response to predetermined settings provided in step 617.The predetermined settings include, a severity threshold, a calculationtime step (time interval between ratio calculations of an intra-cardiacelectrogram) and a channel number of the electrogram signal of amulti-channel (corresponding to multi-electrogram signal) intra-cardiaccatheter. Signal analyzer 19 performs different kinds of signal portionratio analysis in both the time domain (such as of P wave and the Rwave) and frequency domain. In the frequency domain, signal analyzer 19uses different methods of signal portion ratio calculation andcomputation. Signal analyzer 19 tracks a frequency ratio of differentportions of a single heart beat cycle for ventricular tachycardia andfibrillation analysis and discrimination, for example. The ratio offirst frequency peak (dominant frequency, 8-12 Hz) and second frequencypeak (16-24 Hz) is used to capture atrial fibrillation events. Thesignal portion analysis and ratio calculation is not limited andencompasses different ratio ranges and is automatically adaptivelyvaried in response to clinical application and characteristics of acardiac disease.

Signal analyzer 19 calculates a dominant frequency ratio as follows.

${Ratio}_{Dominant\_ frequency} = \frac{{\int_{\varphi}{dominant\_ frequency}}\ }{{\int_{\varphi}{signal\_ frequency}}\ }$

Where, φ is frequency bandwidth of the dominant frequency, e.g. 20-45Hz; φ is a valid signal frequency range, e.g. 1-200 Hz. Signal analyzer19 calculates a principal frequency ratio as follows.

${Ratio}_{Principal\_ frequency} = \frac{{Frequency\_ value}_{first\_ peak}\ }{{Frequency\_ value}_{Second\_ peak}\ }$

Where, the ratio of the first and second frequency peaks correspond totwo significant portions of cardiac signals. Further, variation inprincipal frequency ratio may indicate the occurrence of cardiac events.

In step 621, signal analyzer 19 identifies a particular medicalcondition by mapping determined calculated ratios to corresponding ratiovalue ranges associated with medical conditions using mappinginformation in repository 17. Signal analyzer 19 automaticallyidentifies a particular medical condition indicated by calculated ratiosof electrograms of individual signals of a multi-signal channelintra-cardiac catheter using mapping information associating particularratio value ranges, cardiac location and demographic data (includingage, weight, height, gender and pregnancy status) with cardiacmalfunction and malfunction location and severity in cardiac tissue. Instep 625, analyzer 19 changes calculation time step and steps 613, 621and 625 are automatically iteratively repeated to identify a medicalcondition and associated characteristics for a predetermined limitnumber of iterations. Thereby in step 633 signal analyzer 19 detects andlocalizes an unknown cardiac disease within the cardiac tissue anddetects a malfunction and trend of the malfunction for each electrogramof the multi-signal channel intra-cardiac catheter. Analyzer 19determines location, severity and type of medical condition as well astime of occurrence within a heart cycle. Output processor 36 initiatesgeneration of an alert message for communication in response to acalculated ratio exceeding a predetermined threshold.

FIG. 7 shows an artificial neural network (ANN) 607 employed in signalanalyzer 19 in system 10 (FIG. 1) for heart performance characterizationand multi-signal channel signal ratio analysis for cardiac malfunctionlocalization and severity characterization. Multi-signal channel cardiacsignal ratio analysis provides more precise information about cardiacfunction status and pathology events. System 10 records and comparescalculated signal ratios for signals from different leads of amulti-channel (lead) catheter from different regions of the heart(different tissue, such as atrium, ventricle) and determines ratiovariance used by system 10 together with lead location, in identifyingmalfunction location and severity. Signal analyzer 19 produces asubstantial number of ratio analysis results for a particular heart beatcycle and verifies and combines results for a cardiac event monitoringdecision using an ANN (Artificial Neural Network) system, for example.Signal analyzer 19 performs multi-signal channel signal portion ratioprocessing and computations for ANN data input. Specifically, signalanalyzer 19 provides, time domain segmented cardiac signal ratios 620using surface ECG and intra-cardiac signals and frequency domain ratios623 including dominant frequency ratios and principal frequency ratiosof multi-signal channel electrograms as well as other kinds of signalratios 626 in different domains. ANN unit 607 may alternatively compriseother functions such as a Fuzzy model or expert system model.

ANN unit 607 performs cardiac arrhythmia analysis and detection. The ANN607 calculation and decision module has self-learning capabilityprocessing new input data to increase the accuracy and precision ofcalculated results. ANN unit 607 is trained for versatile diagnosis anddetermination of characteristics including arrhythmia type, severity andtreatment priority categorization. The ANN based ratio analysis isextended to use additional patient information including, patienthistory data, vital signs data, hemodynamic data, and data derived byanalysis and calculation, for example. Thereby the system determinescharacteristics of patient pathologies and cardiac malfunctions.

In the system of FIG. 7 ANN unit 607 maps segmented cardiac time domainsignal ratios 620, frequency domain signal ratios 623 and other ratios626 to candidate diagnosis and treatment suggestions. The ANN unit 607structure comprises 3 layers, an input layer 610, hidden layer 612 andoutput layer 614. ANN unit A_(ij) weights are applied between inputlayer 610 and hidden layer 612 components of the ANN computation andB_(pq) weights are applied between hidden layer 612 and calculationindex components 614 of the ANN computation. The A_(ij) weights andB_(pq) weights are adaptively adjusted and tuned using a training dataset. ANN unit 607 incorporates a self-learning function that processessignal ratios 620, 623 and 626 to increase the accuracy and precision ofcalculated results. ANN unit 607 analyzes input signal ratios byperforming pattern analysis to identify pertinent ratio patterns in aheart chamber, for example, and mapping determined ratio patterns to acandidate diagnosis or treatment decision to localize a tissueimpairment within an organ and determine time of occurrence within aheart cycle. ANN unit 607 also identifies arrhythmia type (e.g., AF, MI,VT, VF), severity of arrhythmia treatment and urgency level and isusable for automatic heart condition detection, diagnosis, warning andtreatment. Further unit 607 performs statistical analysis to construct athreshold used to detect tissue impairment and diagnose and predictcardiac arrhythmia and pathology.

Following a training phase with a training data set, ANN unit 607processes signal ratios 620, 623 and 626 to provide a 3D cardiacelectrophysiological function mapping to data indicating an Arrhythmiatype, Arrhythmia severity, candidate treatment suggestions, localizedtissue impairment information identifying the cardiac arrhythmiaposition, pathology conducting sequence, abnormal tissue area and focusof the disorder and irregularity, for example. System 10 analyzescardiac electrophysiological signals (including ECG and internal cardiacelectrograms) based on a multi-channel and multi-segment signal portionratio calculation and mapping to identify cardiac disorders,differentiate cardiac arrhythmias and quantitative and qualitativeanalysis and characterization of cardiac pathology and events. Theseverity threshold of the pathology decision may vary from person toperson and is adjusted at the beginning of analysis and in oneembodiment may be dynamically adjusted in response to a signal qualityor noise measurement, for example. Since the signal analyzer 19 signalportion ratio calculation and analysis require relatively limitedcomputation power, it may be advantageously utilized in general patientmonitoring, implantable cardiac devices for real time automatic analysisand detection of cardiac arrhythmias and abnormalities.

FIG. 8 shows a flowchart of process performed by system 10 (FIG. 1) forheart performance characterization and abnormality detection. In oneembodiment, the process of FIG. 8 is performed by a system comprising apatient monitoring device. In step 812 following the start at step 811,acquisition device 15 acquires an electrophysiological signalrepresenting heart beat cycles of a patient heart. In step 817, detector34 detects one or more parameters of the electrophysiological signal ofparameter type comprising at least one of, (a) amplitude, (b) timeduration, (c) peak frequency and (d) frequency bandwidth, of multipledifferent portions of a single heart beat cycle of the heart beat cyclesselected in response to first predetermined data. The multiple differentportions of the single heart beat cycle are selected from, a P waveportion, a QRS complex portion, an ST segment portion, a T wave and a Uwave portion in response to second predetermined data. The firstpredetermined data and the second predetermined data comprise at leastone of, (a) default data and (b) data provided in response to usercommand.

In step 819, signal analyzer 19 calculates a ratio of detectedparameters of a single parameter type (e.g., of amplitude, timeduration, peak frequency or frequency bandwidth) of the multipledifferent portions of the single heart beat cycle. Detector 34 detectsmaximum or minimum signal amplitude of the different portions of thesingle heart beat cycle and signal analyzer 19 calculates a ratio ofmaximum signal amplitude or minimum signal amplitude of the differentportions of the single heart beat cycle. Signal analyzer 19 calculates aratio of time duration of a first combination of the multiple differentportions of the single heart beat cycle to a second combination,different to the first combination, of the different portions of thesingle heart beat cycle. Detector 34 further detects maximum or minimumsignal amplitude of a first combination and a second combination of thedifferent portions of the single heart beat cycle and signal analyzer 19calculates a ratio of maximum signal amplitude or minimum signalamplitude of the first combination and the second combination of thedifferent portions of the single heart beat cycle. Further, detector 34detects a peak signal frequency of the first combination and the secondcombination of the different portions of the single heart beat cycle andsignal analyzer 19 calculates a ratio of a peak signal frequency of thefirst combination and the second combination of the different portionsof said single heart beat cycle. In addition, detector 34 detects afrequency bandwidth of the first combination and the second combinationof the different portions of the single heart beat cycle and signalanalyzer 19 calculates a ratio of frequency bandwidth of the firstcombination and the second combination of the different portions of thesingle heart beat cycle.

Detector 34 detects a peak signal frequency of the different portions ofthe single heart beat cycle and signal analyzer 19 calculates a ratio ofpeak signal frequency of the different portions of the single heart beatcycle. Also detector 34 detects a frequency bandwidth of the differentportions of the single heart beat cycle and signal analyzer 19calculates a ratio of frequency bandwidth of the different portions ofthe single heart beat cycle. In step 823, signal analyzer 19 stores inrepository 17, mapping information associating multiple value ranges ofpredetermined calculated ratios with corresponding multiple medicalconditions including arrhythmia, myocardial infarction and myocardialischemia. The medical conditions are determined from a population havingsimilar demographic characteristics to the patient, including age,height, weight, gender and pregnancy status. The mapping informationalso associates the multiple value ranges of predetermined calculatedratios with at least one of, (a) a normal indication and (b) an abnormalindication.

Comparator 31 in step 825 determines whether a calculated ratio exceedsa predetermined upper limit threshold or a predetermined lower limitthreshold and signal analyzer 19 in step 827 uses the mappinginformation in automatically identifying a particular medical conditionindicated by a calculated ratio or a ratio value range identified by thedetermination of step 825. In step 829 output processor 36 generatesdata representing an alert message in response to a calculated ratioexceeding a predetermined threshold or a predetermined combination ofcalculated ratios exceeding a predetermined threshold. The alert messageinitiates treatment by at least one of, (a) initiating drug delivery and(b) initiating electrical stimulus or pacing of a heart. The alertmessage also indicates severity of a cardiac condition and providesadvance warning of myocardial ischemia or acute myocardial infarction incases including non-symptomatic cases. The process of FIG. 8 terminatesat step 831.

The system and processes of FIGS. 1-8 are not exclusive. Other systems,processes and menus may be derived in accordance with the principles ofthe invention to accomplish the same objectives. Although this inventionhas been described with reference to particular embodiments, it is to beunderstood that the embodiments and variations shown and describedherein are for illustration purposes only. Modifications to the currentdesign may be implemented by those skilled in the art, without departingfrom the scope of the invention. The system employs cardiac signalportion ratio analysis of cardiac electrophysiological signals and usespredetermined mapping information to associate particular ratio valuesto a corresponding particular medical condition and determine anaccurate time, location and severity of cardiac pathology and events.Further, the processes and applications may, in alternative embodiments,be located on one or more (e.g., distributed) processing devices on thenetwork of FIG. 1. Any of the functions and steps provided in FIGS. 1-8may be implemented in hardware, software or a combination of both.

1. A system for heart performance characterization and abnormalitydetection, comprising: an acquisition device for acquiring anelectrophysiological signal representing heart beat cycles of a patientheart; a detector for detecting one or more parameters of saidelectrophysiological signal of parameter type comprising at least oneof, (a) amplitude, (b) time duration, (c) peak frequency and (d)frequency bandwidth, of a plurality of different portions of a singleheart beat cycle of said heart beat cycles selected in response to firstpredetermined data, said plurality of different portions of said singleheart beat cycle being selected from, a P wave portion, a QRS complexportion, an ST segment portion and a T wave portion in response tosecond predetermined data; a signal analyzer for calculating a ratio ofdetected parameters of a single parameter type of said plurality ofdifferent portions of said single heart beat cycle; and an outputprocessor for generating data representing an alert message in responseto a calculated ratio exceeding a predetermined threshold.
 2. A systemaccording to claim 1, wherein said different portions of said singleheart beat cycle include a U wave portion.
 3. A system according toclaim 1, including a comparator for determining whether a calculatedratio exceeds a predetermined upper limit threshold or a predeterminedlower limit threshold.
 4. A system according to claim 1, including arepository of mapping information associating a plurality of valueranges of predetermined calculated ratios with a corresponding pluralityof medical conditions, said signal analyzer uses said mappinginformation in automatically identifying a particular medical conditionindicated by a calculated ratio and said alert message identifies saidparticular medical condition.
 5. A system according to claim 4, whereinsaid mapping information associates said plurality of value ranges ofpredetermined calculated ratios with at least one of, (a) a normalindication and (b) an abnormal indication.
 6. A system according toclaim 4, wherein said plurality of medical conditions include at leasttwo of, (a) arrhythmia (b) myocardial infarction and (c) myocardialischemia.
 7. A system according to claim 4, wherein said mappinginformation associates a plurality of value ranges of predeterminedcalculated ratios with a corresponding plurality of medical conditionsdetermined from population having similar demographic characteristics tosaid patient, said demographic characteristics including at least two ofage, height, weight, gender and pregnancy status.
 8. A system accordingto claim 1, wherein said first predetermined data and said secondpredetermined data comprise at least one of, (a) default data and (b)data provided in response to user command.
 9. A system for heartperformance characterization and abnormality detection, comprising: anacquisition device for acquiring an electrophysiological signalrepresenting heart beat cycles of a patient heart; a detector fordetecting time duration of a plurality of different portions of a singleheart beat cycle of said heart beat cycles selected in response to firstpredetermined data, said plurality of different portions of said singleheart beat cycle being selected from, a P wave portion, a QRS complexportion, an ST segment portion and a T wave portion in response tosecond predetermined data; a signal analyzer for calculating a ratio oftime duration of said plurality of different portions of said singleheart beat cycle; and an output processor for generating datarepresenting an alert message in response to a calculated ratioexceeding a predetermined threshold.
 10. A system according to claim 9,wherein said detector detects maximum or minimum signal amplitude ofsaid different portions of said single heart beat cycle and said signalanalyzer calculates a ratio of maximum signal amplitude or minimumsignal amplitude of said different portions of said single heart beatcycle.
 11. A system according to claim 9, wherein said detector detectsa peak signal frequency of said different portions of said single heartbeat cycle and said signal analyzer calculates a ratio of peak signalfrequency of said different portions of said single heart beat cycle.12. A system according to claim 9, wherein said detector detects afrequency bandwidth of said different portions of said single heart beatcycle and said signal analyzer calculates a ratio of frequency bandwidthof said different portions of said single heart beat cycle.
 13. A systemaccording to claim 9, wherein said different portions of said singleheart beat cycle include a U wave portion.
 14. A system according toclaim 9, wherein said output processor generates data representing analert message in response to a predetermined combination of calculatedratios exceeding a predetermined threshold.
 15. A system according toclaim 9, wherein said system comprises a patient monitoring device. 16.A system according to claim 9, wherein said alert message indicatesseverity of a cardiac condition.
 17. A system according to claim 9,wherein said alert message provides advance warning of myocardialischemia or acute myocardial infarction in cases includingnon-symptomatic cases.
 18. A system according to claim 9, wherein saidalert message initiates treatment by at least one of, (a) initiatingdrug delivery and (b) initiating electrical stimulus or pacing of aheart.
 19. A method for heart performance characterization andabnormality detection, comprising the activities of: acquiring anelectrophysiological signal representing heart beat cycles of a patientheart; detecting time duration of a plurality of different portions of asingle heart beat cycle of said heart beat cycles selected in responseto first predetermined data, said plurality of portions of said singleheart beat cycle being selected from, a P wave portion, a QRS complexportion, an ST segment portion and a T wave portion in response tosecond predetermined data; calculating a ratio of time duration of afirst combination of said plurality of different portions of said singleheart beat cycle to a second combination, different to said firstcombination, of said different portions of said single heart beat cycle;and generating data representing an alert message in response to acalculated ratio exceeding a predetermined threshold.
 20. A methodaccording to claim 19, wherein said activity of detecting time durationcomprises detecting maximum or minimum signal amplitude of said firstcombination and said second combination of said different portions ofsaid single heart beat cycle and said activity of calculating a ratiocomprises calculating a ratio of maximum signal amplitude or minimumsignal amplitude of said first combination and said second combinationof said different portions of said single heart beat cycle.
 21. A methodaccording to claim 19, wherein said activity of detecting time durationcomprises detecting a peak signal frequency of said first combinationand said second combination of said different portions of said singleheart beat cycle and said activity of calculating a ratio comprisescalculating a ratio of a peak signal frequency of said first combinationand said second combination of said different portions of said singleheart beat cycle.
 22. A method according to claim 19, wherein saidactivity of detecting time duration comprises detecting a frequencybandwidth of said first combination and said second combination of saiddifferent portions of said single heart beat cycle and said activity ofcalculating a ratio comprises calculating a ratio of frequency bandwidthof said first combination and said second combination of said differentportions of said single heart beat cycle.